This invention relates to steam generators for nuclear power plants and more particularly to steam gnerators having vertical tubesheets.
Significant localized corrosion of tubes has been found in a substantial number of pressurized water reactor vertical steam generators after several years of operation. This corrosion has occurred on the outer side of the tubes immediately above the tubesheet in areas where substantial deposits of solids or crud have accumulated. It is believed that the corrosion experienced results from the accumulation of crud deposits on the horizontal tubesheet as the tube temperature in the affected area increases to such a degree that steam blanketing and/or chemical concentration occur adjacent the tubes and increase the corrosion rate to such an extent as to cause thinning of the tube walls and premature failure of the tubes. Eliminating these deposits adjacent the tubes will increase the life of the tubes substantially.